This would severely hamper his carefully constructed plan to grab a child from the street and take her back to his flat.
He did not know when he would get another chance, and cruising round a South Coast town shortly before 9am on Tuesday, 19 January, he was desperate.
Then he saw them. Two little girls on their way to school, bags over their shoulders, laughing and joking with the shared complicity of 10- year-olds. The street was narrow and they were walking in the road. Hopkinson stopped the car, jumped out and one of the girls happened to ask him the time.
He grabbed them both and forced them into the boot of the turquoise Vauxhall Corsa so quickly they didn't have time to scream. Astonishingly, no one else saw what had happened.
Later that afternoon he carried the children one at a time up to his flat in a large black sports bag. Yet just two weeks earlier, Sussex police had visited him, as they had the previous year, and warned him again about his reported behaviour. But without evidence all they could do was warn him and tell him that entertaining young children in his flat was "inappropriate".
But as Detective Superintendent Jeremy Paine was telling a packed press conference the following morning that he suspected the girls may have run away, fellow officers in Eastbourne were gathering evidence against Hopkinson and preparing to have him listed on the sex offenders register after a complaint by a child.
But, almost incredibly, officers did not liaise with each other. Had they done so, the girls may have been found much sooner. At that stage no one suspected Hopkinson of abduction for several reasons, one being that he was outside the five-mile radius in which kidnappers usually operate.
"I was fairly sure when we gave the press conference on the Wednesday morning that the girls would have been found by the afternoon," Mr Paine said.
By that evening there were more than 300 police searching for them as well as 50 Gurkhas and military police from nearby barracks. As the search was extended, they knocked on doors, searched in deserted buildings, and burrowed in hedges. Detectives were checking the list of registered sex offenders.
"We had to prioritise and we had 500 houses in the block between the school and their homes," said Mr Paine. There were 100 people with convictions of assault and 36 people on the sex offenders register in the area. They all had to be checked before the search was widened to other towns.
"At that stage abduction was not the strongest theory and there had been a lot of reported sightings," said Mr Paine. By the Friday morning, he had to admit there was a real possibility the children were dead. But even as he spoke to the assembled reporters, the news was coming through that they had been found.
Detective Sergeant Doug Bick, head of Eastbourne child protection unit, had been at home in Hastings when he finally remembered Hopkinson and the investigation for which the police had planned an arrest. DS Bick rang his station and suggested they arrest him on the Friday morning.
He and Detective Constable Martin Toft, with three uniformed policemen, went to Hopkinson's flat. Hopkinsonsaid he had to get dressed and asked them to return later. But he eventually let them in. The girls were sitting on a single bed in front of the television in the lounge. There were no handles on their side of the door.
DS Bick said: "His activities were being monitored as best we could but until he committed an offence all we could do is monitor. He is not the only paedophile who has abducted a child and it happened a long way from where he was living. You could probably have thrown several individuals into play.
"Yes, he did have a previous conviction for abduction but, in the absence of any specific intelligence that the children were there, we acted as quickly as we could have done."
As Hopkinson was interviewed over the next few days, officers learnt that Hopkinson had made maps in prison with the names of schools and routes to reach them marked in red ink, with names of children he had culled from the local newspaper.
Mr Paine maintains that his team conducted the investigation correctly. "We were right in what we did," he said. "We had to prioritise our search and you have to search a premises properly if you are going to do it at all.
"The lesson we have learnt is that in future we could send out the child protection teams to knock on doors in nearby towns straightaway."